Check untaxed interest figure

How can I check the untaxed interest figure on my tax code notice? The letter states 'log in to your personal tax account to see the interest we have included' but I can't find the information or a breakdown anywhere.

Hi
If there is no option to view the income or a breakdown online, you will need to contact the helpline or write to us to query the amount shown in the coding.
Income Tax: general enquiries

Does anyone have any advice on how successful an enquiry has been?

I called the helpline today about this, and they were very helpful. They read out a list of every account I had, and how much interest had been reported to them.